Bifocals

Bifocals are eyeglasses with an upper and lower half, the upper for distance, and the lower for reading. Bifocals are commonly prescribed to people with presbyopia, a condition that Franklin suffered. Franklin wrote, in August 1784 to his friend George Whatley, that he was "happy in the invention of double spectacles, which serving for distant objects as well as near ones, make my eyes as useful to me as ever they were."